These middle grade books will feature characters from two of Riordan’s earlier series: Percy Jackson & The Olympians and The Heroes of Olympus. The story is set in both Camp Half-Blood and Camp Jupiter. The first installment, entitled The Hidden Oracle, will be released on May 03, 2016.
Here’s more from Riordan’s blog post: “As I explained on tour, the idea came to me while writing Percy Jackson’s Greek Gods, because Apollo had been turned mortal twice before when he got on Zeus’ bad side. The first novel has been so much fun to write! The Trials of Apollo is told first person from Apollo’s point of view.”